Peptides, method for assaying human pepsinogen II or human pepsin II, and assaying kit

ABSTRACT

A peptide of the formula (I)                    
     (wherein each symbol is as defined in the description.) or an acid addition salt thereof. 
     A compound of the formula (I) is a specific substrate for human pepsin II, so it can be used for assaying human pepsin II or human pepsinogen II and it is useful for diagnosis of gastric diseases such as gastric cancer and gastric ulcer.

FIELD OF THE INVENTION

The present invention relates to a method for assaying human pepsin II or human pepsinogen II in the human body fluid (such as gastric juice, blood, urine etc.) as diagnostic marker of gastric diseases such as gastric cancer, gastric ulcer etc. and a peptide used as a substrate in such a method.

More detailed, the present invention relates to

1) a peptide of the formula (I)

(wherein, Q is Q^(a)—(AA)n— (in which AA is L-amino acid, n is 0 or an integer of 1˜15, Q^(a) is hydrogen, C1˜4 alkyl, an amino-protective group, D- or L-amino acid residue or NH₂—(CH₂)r—CO— (in which r is an integer of 2˜7.).),

R¹ and R² are (i) hydrogen or halogen or, (ii) R¹, R² and unsaturated bond together form an aromatic carbon ring may be substituted by halogen,

R³ is hydrogen or halogen,

R⁴ is hydrogen, C1˜3 alkyl or hydroxymethyl,

EE is D- or L-amino acid residue,

m is 0 or 1,

Z is an aniline derivative residue, an aminocoumarine derivative residue or an aminonaphthalene derivative residue,

with the proviso that (1) when n is 2 or more, each AA is same or different, and that (2) the compounds wherein all of R¹, R² and R³ is hydrogen are excluded.)

or an acid addition salt thereof and,

2) a method for assaying human pepsinogen II or human pepsin II which is characterized by digesting a peptide of the formula (I) (wherein all the symbols are as defined hereinbefore.) described in the said 1) or an acid addition salt thereof by human pepsin II which is obtained by activation of human pepsinogen II in a sample or human pepsin II in a sample to obtain an amino acid derivative of the formula (II)

(wherein all the symbols are as defined hereinbefore.),

digesting the obtained amino acid derivative by aminopeptidase to obtain an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H and then

detecting the obtained aniline, aminocoumarine or aminonaphthalene derivative and

3) a kit for assaying human pepsinogen II or human pepsin II which is characterized by comprising a peptide of the formula (I) (wherein all the symbols are as defined hereinbefore.) described in the said 1) or an acid addition salt thereof as a substrate and an aminopeptidase.

BACKGROUND

It is known that the pepsinogen secretion is parallel to gastric acid secretion and that human serum or urine pepsinogen levels are also parallel to gastric pepsinogen secretion. The above pepsinogen exists as pepsinogen in the body fluid such as blood or urine except for gastric juice, on the other hand, it exists as pepsin in gastric juice.

It is said that human blood or urine pepsinogen I level of the patient with atrophic gastritis decreases and that human blood or urine pepsinogen I and pepsinogen II levels increase in case of gastric ulcer (Japanese Patent Application Kokai Hei 7-304800). In addition, it is said that both pepsinogen I level and pepsinogen II/I ratio decrease in the patient with gastric cancer (Jpn. J. Cancer Res., 80, 111-114 (1989)).

Further, an attention is paid to serum pepsinogen II level and pepsinogen I/II ratio as markers of therapy for helicobacter pylori gastritis. That is to say, it is said that serum pepsinogen II level decreases significantly and pepsinogen I/II ratio increases significantly in a successful group consisting of patients in whom therapy resulted in eradication of the bacteria to compare with an unsuccessful group consisting of patients who remained infected (Prog. Med., 15, 1862-1868 (1995)).

Therefor, assaying the level of human pepsinogen II in human blood or urine may be useful for diagnosis at early stage of diseases such as gastric cancer, gastric ulcer and duodenal ulcer etc.

As for a method for assaying human pepsin which was obtained by activation of human pepsinogen, a method using human serum protein etc. in urine and serum based on its digesting activity has been known (Clin. Chem., 15, 1, 42-55 (1969)). The significance of clinical trial using such a method has been discussed, but it requires a long time. In addition, its accuracy was not good, so such a method has been of no practical use. Further, the results means the activity to digest protein, so it was reflected on the total activities of both pepsin I and pepsin II. Therefore it is impossible to determine the human serum pepsinogen II specifically.

Recently, a method for assaying human pepsinogen in urine (uropepsin) indirectly, based on inactivation of an acidic enzyme by activated pepsin was proposed (Japanese Patent Application Kokai Hei 7-155198). But the substrate used in this method did not show the specificity for pepsin II. It is said that the pepsinogen in urine is pepsinogen I. But, pepsin II may be also secreted in urine in some body condition, so it is difficult to determine the accurate level of pepsin II. It is impossible to assay the level of pepsinogen II in human serum specifically.

As for a method for assaying pepsinogen II, radio immunoassay (Kaku-igaku (in Japanese), Vol. 26, No. 9, 1217-1221 (1989)) and enzyme immunoassay (Japanese Patent Application Kokai Hei 7-304800) using a specific anti-body have been practical use, but these methods cause a radioactive pollution and require a long time and complicated procedure for assaying.

Some methods for assaying pepsin II using synthesized substrate have been proposed. For example, (A) in the paper of J. Med., Chem., 36, 2614 (1993), it was described that a peptide of the formula (A-1)

LysProAlaAlaPhePhe(NO₂)ArgLeu   (A-1) (SEQ ID NO:86)

(wherein Phe(NO₂) is p-nitrophenylalanine.)

was used as a substrate in assaying inhibitory effect of some compounds on human pepsin II. That is to say, a peptide of the formula (A-1) was digested by human pepsin II to obtain a peptide of the formula (A-2)

Phe(NO2)ArgLeu  (A-2)

(wherein Phe(NO2) is as defined hereinbefore.),

and the obtained peptide of the formula (A-2) was used in the assaying inhibitory activity on enzyme based on decrease of absorbance at 234˜324 nm as an index.

But this paper did not disclose that such a peptide of the formula (A-1) may be as a substrate for human pepsin II. Therefore, it is uncertain whether this peptide has specificity for human pepsin II, or not. In addition, the chromophore of this peptide is Phe(NO₂), so it is expected that the accuracy of the method using this peptide is one tenth or less to compare with p-nitroaniline (abbreviated as pNA). Further, it is impossible to be used in automated clinical analyzer due to detection at 234˜324 nm.

(B) in the paper of J. Biochem., 265, 871-878 (1990), it was described that a peptide of the formula (B-1)

LysProValValPhePhe(NO₂)ArgLeu  (B-1) (SEQ ID NO:87)

(wherein Phe(NO₂) is as defined hereinbefore.),

was used as a substrate in assaying inhibitory effect of some compounds on human pepsin II. That is to say, a peptide of the formula (B-1) was digested by human pepsin II to obtain a peptide of the formula (B-2)

Phe(NO2)ArgLeu  (B-2)

(wherein Phe(NO₂) is as defined hereinbefore.),

and the obtained peptide of the formula (B-2) was used in the assaying inhibitory activity on enzyme based on decrease of absorbance at 234˜324 nm as an index.

But this paper did not disclose that such a peptide of the formula (B-1) may be as a substrate for human pepsin II. Therefore, it is uncertain whether this peptide has a specificity for human pepsin II, or not. In addition, the chromophore of this peptide is Phe(NO₂), so it is expected that the accuracy of the method using this peptide is one tenth or less to compare with p-nitroaniline (abbreviated as pNA). Further, it is impossible to be used in automated clinical analyzer due to detection at 234˜324 nm (There are the same problems as in paper (A).).

(C) In CS-261172, it was described that a peptide of the formula (C-1)

X—A—B-Phe-D-pNA  (C-1)

(wherein X is hydrogen, C3˜5 carboxylalkylcarbonyl or C1˜5 alkylcarbonyl,

A is pyroglutamic acid (abbreviated as pGlu), Asp, Glu or Gly residue or 2-oxoimidazoline-1-yl-carbonyl,

B is His, Gly or Pro residue,

D is Phe, Leu, Nle, Met or S—C1˜3 alkyl-Cys residue, and pNA is p-nitroaniline residue.)

was used as a substrate in assaying activities of pepsin I, pepsin II and chymosin.

But, there was neither description nor suggestion about the specificity of this peptide for human pepsin II.

In the example, a peptide of the formula (C-2)

pGluHisPhePhe-pNA  (C-2) (SEQ ID NO:88)

(wherein pGlu and pNA are as defined hereinbefore.)

was used in assaying activity of pig pepsin. This pig pepsin was not purified and thought to be a mixture of pepsin I and pepsin II. So, it is not expected that this substrate possesses a specificity for human pepsin II.

(D) In the paper of Clinica Chimica Acta 213, 103-110 (1992), it was described that a peptide of the formula (D-1)

X^(d)—(AA^(d))n^(d)-Phe-D^(d)-pNA  (D-1)

(wherein X^(d) is pGlu, Glt, AA^(d) is sequence for a substrate for N-termini, n^(d) is 1 or 2, D^(d) is Phe, Nle or Met and the other symbols are as defined hereinbefore.)

was used as a substrate in assaying activities of pepsin I, pepsin II and chymosin.

But, there was neither description nor suggestion about the specificity of this peptide for human pepsin II.

In the experimental example, a peptide of the formula (D-2) or (D-3)

pGluHisPhePhe-pNA   (D-2) or (SEQ ID NO:90)

pGluHisPheMet-pNA   (D-3) (SEQ ID NO:91)

(wherein pGlu and pNA are as defined hereinbefore.)

was used as a substrate in assaying activities of pig pepsin. This pig pepsin was not purified and thought to be a mixture of pepsin I and pepsin II. So, it is not expected that this substrate possesses a specificity for human pepsin II.

(E) In the paper of Anal. Biochem., 234, 113 (1996), it was described that peptides of the formula (E-1) or (E-2)

AbzAlaAlaPhePheAlaAla-Ded  (E-1), or (SEQ ID NO:92)

AbzAlaAlaPhePheAlaAla-pNA  (E-2) (SEQ ID NO:93)

(wherein Abz is o-aminobenzoyl, Ded is N-2,4-dinitrophenylethylene-diamine and pNA is as defined hereinbefore.), were used as substrate in assaying activities of human pepsin I, human pepsin II, human cathepsin D and HIV protease by fluorophotometry.

In this paper, the fluorescent changes caused by modification of peptide was discussed. Particularly, a peptide of the formula (E-1) seemed to be suggested to have specificity for human pepsin I from the experimental result. But, the peptides of the formula (E-1) or (E-2) were not expected to have the specificity for human pepsin II.

(F) In the paper of J. Biol. Chem., 244, 5, 1085-1091 (1969), it was described that peptides of the formula (F-1)˜(F-5)

Z-TyrAla  (F-1),

Z-TyrThr  (F-2),

Z-TyrLeu  (F-3),

Z-TyrSer  (F-4) or

Z-TrpAla  (F-5)

(wherein Z is benzyloxycarbonyl.)

were used as substrate in assaying activities of human pepsin II specifically. But it requires a long time and complicated procedure. In addition, its accuracy was not good, so such a method has been of no practical use.

The substrates described in the said five references (A)˜(F) are distinct from the substrate (peptide) of the present invention entirely. That is to say, there is a structural characteristic that an amino acid of the formula

(wherein all the symbols are as defined hrereinbefore.) in the peptide of the formula (I) of the present invention is not an essential amino acid (for example, Phe, Tyr) but phenylalanine substituted by halogen or 2-naphthylalanine (in which naphthyl may be substituted by halogen.). Such a group was neither described nor suggested in the said six references (A)˜(F).

DISCLOSURE OF THE INVENTION

The present inventors have been studying to dissolve these problems of the related arts and to find a substrate which is high-sensitive (being high rate of enzyme reaction i.e., digesting a substrate by human pepsin II at a high rate and/or being able to produce efficient coloring) and specific for human pepsin II, and then have succeeded in synthesizing a substrate (peptide) which is sensitive and specific for human pepsin II. By using this substrate, it become to possible to determine pepsin II for short time to compare with the method of related arts and to determine pepsinogen II and pepsin II using automated clinical analyzer.

That is to say, the present invention relates to

1) a peptide of the formula (I)

(wherein all the symbols are as defined hereinbefore.), or acid addition salt thereof,

2) a method for assaying human pepsinogen II or human pepsin II characterized by

digesting a peptide of the formula (I) described in the above 1) (wherein all the symbols are as defined hereinbefore.), or an acid addition salt thereof, by human pepsin II which is obtained by activation of human pepsinogen II in a sample or human pepsin II in a sample to obtain an amino acid derivative of the formula (II)

(wherein all the symbols are as defined hereinbefore.),

digesting the obtained amino acid derivative by aminopeptidase to obtain an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H and then

detecting the obtained aniline, aminocoumarine or aminonaphthalene derivative,

3) a kit for assaying human pepsinogen II or human pepsin II which is characterized by comprising a peptide of the formula (I) described in the above 1), or an acid addition salt thereof as a substrate and aminopeptidase.

BRIEF EXPLANATION OF FIGURE

FIG. 1 shows calibration curve between pepsinogen II level (ng/ml) and the plotted increase of absorbance in Example 4.

FIG. 2 shows correlation between a conventional method for assaying serum pepsinogen II (RIA) using a kit for assaying pepsinogen II (marketed from Dinabott Co), and a method for assaying of the present invention. The values on the abscissa and ordinate indicate the detected value (ng/ml) determined by RIA method and the increase of absorbance determined by the method of the present invention, respectively.

FIG. 3 shows calibration curve between pepsinogen II level (ng/ml) and the plotted increase of absorbance in Example 6.

FIG. 4 shows correlation between a conventional method for assaying serum pepsinogen II (RIA) using a kit for assaying pepsinogen II (marketed from Dinabott Co), and a method for assaying of the present invention. The values on the abscissa and ordinate indicate the detected value (ng/ml) determined by RIA method and the increase of absorbance determined by the method of the present invention, respectively.

DETAILED EXPLANATION OF THE INVENTION

A sample as an objet in the present invention means any sample to be determined the concentration of human pepsinogen II and activity of human pepsin II. For example, such a sample includes human body fluid (such as gastric juice, blood or urine etc.). The above pepsinogen II (pepsin II) exists as form of pepsinogen II in the body fluid such as blood or urine except for gastric juice, on the other hand, it exists as form of pepsin II in gastric juice.

The abbreviation consisting of three characters in the present invention means an amino acid (unless specified, it means L-type of α-amino acid.) well known and its definition is as follows:

Gly=glycine,

Ala=alanine.

Val=valine

Leu=leucine,

An amino-protective group represented by Q^(a) in Q includes, for example, C1˜6 alkylcarbonyl, C1˜6 alkylsulfonyl, benzyloxycarbonyl, tert-butoxycarbonyl, 9-fluorenylmethoxycarbonyl or benzoyl or its derivative (in which benzene ring in benzyloxycarbonyl or benzoyl is unsubstituted or substituted by 1˜5 of substituent(s) selected from the group consisting of nitro, amino, amino gourd substituted by one or two C1˜6 alkyl, C1˜6 hydroxyalkylamino, carboxyl, hydroxy, halogen, C1˜6 alkyl, C1˜6 alkoxy, thiol, sulfonyl, C1˜6 alkylsulfonyl, —CH₂CH₂COOH and —CH═CH—COOH).

A group of NH₂—(CH₂)r—CO— represented by Q^(a) in Q includes β-aminopropionic acid residue (β-Ala-), γ-aminobutanoic acid residue (γ-Abu-), δ-aminopentanoic acid residue, δ-aminocapronic acid residue, 6-aminoheptanoic acid residue, 7-aminooctanoic acid residue.

Amino acid residue represented by AA and EE in Q includes twenty essential amino acid (Gly, Ala, Val, Leu, lie, Ser, Thr, Asp, Glu, Asn, Gin, Lys, Arg, Cys, Met, Phe, Tyr, Trp, His, Pro) residue.

In these amino acids,

1) Gly, Ala, Val, Leu, lie, Ser, Thr, Asp, Glu, Asn, Gin, Lys, Arg, Cys, Met are aliphatic amino acids,

2) Phe, Tyr are aromatic amino acids,

3) Trp, His, Pro are heterocyclic amino acids.

In the aliphatic amino acid of 1),

a) Val, Leu, Ile are branched amino acids,

b) Ser, Thr are hydroxy amino acids,

c) Asp, Glu are acidic amino acids,

d) Asn, Gln are amides,

e) Lys, Arg are basic amino acids,

f) Cys, Met are S-containing amino acids.

Preferably, Q includes polypeptide of Q^(b)—(M)s—A¹— (in which A¹

IIe=isoleucine,

Ser=serine,

Thr=threonine,

Asp=aspartic acid,

Glu glutamic acid,

Asn=asparagin

Gln=gulutamine

Lys=lysine,

Arg=arginine,

Cys=cystein,

Met=methionine,

Phe=phenylalanine,

Tyr=tyrosine,

Trp=triptophane,

His=histidine,

Pro=proline.

As for the other abbreviation, its definition is as follows:

Sar=N^(α)-methyl-glycine,

Me-Val=N^(α)-methyl-valine,

Me-Ala=N^(α)-methyl-alanine,

Nle=norleucine,

γ-Abu=γ-aminobutanoic acid,

Glt=glytaryl (—CO(CH₂)₃CO—),

pNA=p-nitroaniline residue,

Ac=acetyl,

3,4-DCP=3,4-dichlorophenyl,

m-ASD=m-anisidine residue,

DCHA=3,5-dichloro-4-hydroxyaniline residue.

C1˜4 alkyl represented by Q^(a) in Q and Q^(b) described hereinafter includes methyl, ethyl, propyl or butyl, or isomer thereof.

is Gly, Ala, Ser, Asp, Glu, Asn, Gin or Met residue, s is an integer of 2, 3, 4 or 5, Q^(b) is hydrogen, C1˜4 alkyl, C1˜6 alkylcalbonyl, D- or L-amino acid residue or NH₂—(CH₂)r—CO— (in which r is as defined hereinbefore.), each AA is as defined hereinbefore.), more preferably, polypeptide of Q^(b)—(M)t—A²—A¹¹— (in which A¹¹ is Gly, Ala, Glu, Asn residue, A² is Gly, Ala, Leu, Ser, Asp, Glu, Asn or Gin residue, t is an integer of 1, 2, 3 or 4, Q^(b) and each AA are as defined hereinbefore.), most preferably, polypeptide of Q^(b)—(AA)t—A²²—A¹¹— (in which A¹¹ is Gly, Ala, Glu or Asn residue, A²² is Gly, Ser, Glu or Gin residue, t, Q^(b) and each AA are as defined hereinbefore.).

Aromatic carbon ring formed by R¹, R² and unsaturated bond together includes benzene or naphthalene ring, more preferably, benzene ring.

Each m is preferable.

An aniline, aminocoumarine or aminonaphthalene derivative represented by Z—H means unsubstituted aniline, unsubstituted aminocoumarin, and unsubstituted aminonaphthalene or substituted ones wherein benzene ring, coumarin ring, naphthalene ring in each group is substituted by 1˜5 of substituent(s) selected from the group consisting of nitro, amino, amino gourd substituted by one or two C1˜6 alkyl, C1˜6 hydroxyalkylamino, carboxyl, hydroxy, halogen, C1˜6 alkyl, C1˜6 alkoxy, thiol, sulfonyl, C1˜6 alkylsulfonyl, —CH₂CH₂COOH and —CH═CH—COOH. Preferably, the number of such substituent(s) is 1, 2 or 3.

C1˜6 alkyl in the explanation of the said aniline, aminocoumarine or aminonaphthalene derivative represented by Z—H and amino-protective group represented by Q^(a) in Q, C1˜6 alkyl in C1˜6 alkylcarbonyl (including C1˜6 alkyl represented by Q^(b) described hereinafter) or C1˜6 alkyl in C1˜6 alkylsulphonyl and C1˜6 hydroxyalkylamino includes methyl, ethyl, propyl, butyl, pentyl or hexyl, or isomer thereof.

C1˜6 alkoxy in the explanation of the said aniline, aminocoumarine or aminonaphthalene derivative represented by Z—H and amino-protective group represented by Q^(a) in Q, includes methoxy, ethoxy, propoxy, butoxy, pentyloxy or hexyloxy, or isomer thereof.

Aniline derivative represented by Z—H includes, for example, p-nitroaniline, m-anisidine, 3,5-dichloro-4-hydroxyaniline, 3,5-dibromo-4-hydroxyaniline, N′,N′-diethylphenylenediamine or 3-carboxyl-4-hydroxyaniline.

Aminocoumarine derivative or aminonaphthalene derivative represented by Z—H includes, for example, 7-amino-4-methylcoumarin, 4-methyl-2-aminonaphthalene, or 4-methoxy-2-aminonaphthalene.

Preferably, group represented by Z—H includes, for example, p-nitroaniline, m-anisidine, 3,5-dichloro-4-hydroxyaniline, 7-amino-4-methylcoumarin, 4-methyl-2-aminonaphthalene, or 4-methoxy-2-aminonaphthalene. More preferably, it includes p-nitroaniline, m-anisidine or 3,5-dichloro-4-hydroxyaniline.

The peptide of the present invention may be converted into the corresponding acid additional salts. Water-soluble salts are preferable. Suitable acid addition salts, for example, are salts of inorganic acids, e.g., such as hydrochloric acid, hydrobromic acid, phosphonate, sulphonate, nitric acid etc., or salts of organic acids, e.g., succinate, citrate, lactate, malate, benzenesulfonate, acetate, trifluoroacetate or trifluoromethansulfate etc. Trifluoroacetate or trifluoromethansulfate are preferable.

Process for Preparing Peptides of the Present Invention

A peptide used as a substrate in the present invention may be prepared by the well-known methods in chemical synthesis of peptide. For example, as shown in Reaction scheme 1 or examples described hereinafter, a peptide of the present invention may be prepared by reacting resin to be solid phase (e.g., oxymresin) with an amino acid of the formula (III)

(in which Q^(d) is an amino-protective group and the other symbols are as defined hereinbefore.), and then, by coupling reaction of the obtained compound with amino acid successively.

Further, as shown in Reaction scheme 2, a peptide of the present invention may be prepared by reacting an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H as chromophore with an amino acid of the formulae (IV-1) or (IV-2)

(wherein each Q^(aa) and Q^(bb) is an amino-protective group and the other symbols are as defined hereinbefore.), by coupling the obtained compound with an amino acid successively and by separating the aimed peptide from resin finally, if desired, followed by removal of protective group, or by coupling a few amino acids each other to obtain a few kind of polypeptides and then by coupling such a few kind of polypeptides successively.

(in Reaction scheme 1, each Q^(d), Q¹, Q² and Q^(n) is an amino-protective group, OxR is oxymresin, each AA¹, AA² and AA^(n) is an amino acid residue and the other symbols are as defined hereinbefore. In addition, each reaction in parentheses of (condensing), (Removal of Q¹) etc. is optional reaction.)

(in Reaction scheme 2, each Q^(aa), Q^(bb), Q^(cc), Q¹, . . . Q^(n) is an amino-protective group and the other symbols are as defined hereinbefore. In addition, each reaction in parentheses of (condensing), (Removal of Q¹) etc. is optional reaction.)

In the above coupling or reaction, amino and carboxyl group which does not relate to the reaction directly is protected by a protective group used ordinary in synthesizing a peptide. An amino-protective group represented by Q^(d), Q¹, Q², Q^(n), Q^(aa), Q^(bb) and Q^(cc) includes, for example, benzyloxycarbonyl (CBZ), tert-butoxycarbonyl (Boc) or 9-fluorenylmethoxycarbonyl (Fmoc) etc. When an Arg or Lys is used in reaction, a δ-guanidino and ε-amino group in Arg and Lys, respectively, is protected by a protective group. A carboxyl-protective group represented by Rc includes, for example, ester group such as benzyl or tert-butyl ester etc. When Glu is used in reaction, the carboxyl group in the side chain is protected by a protective group. Each protective group is removable by the known method after reaction.

The coupling reaction of chromophore and amino acid may be carried out by the methods known per se, for example,

(1) by the method using acid halide

(2) by the method using mixed acid anhydride

(3) by the method using conducing agent (EDC, PyBrop, DCC etc.)

Concrete description of the methods described above are as follows:

(1) method using acid halide may be carried out, for example, amino acid in which an amino group is protected (for example, amino acid of the formula Q¹—AA¹—OH, Q²—AA²—OH, Q^(n)—AA^(n)—OH etc.) is reacted with an acid halide (oxalyl chloride or thionyl chloride etc.) in an inert organic solvent (chloroform, methylene chloride, diethylether or THF (tetrahydrofuran) etc.) or without solvents at from −20° C. to a refluxing temperature to give an acid halide. The obtained acid halide and an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H or a (poly)peptide prepared by coupling of the corresponding compound and then by removing an amino-protective group (for example, a (poly)peptide of the formula H—EE—Z or the formula

etc.) are reacted in an inert organic solvent (chloroform, methylene chloride, diethylether, THF etc.) in the presence of tertiary amine (pyridine, triethylamine, dimethylaniline, dimethylaminopyridine, diisopropylethylamine etc.) at 0˜40° C.

(2) method using mixed acid anhydride may be carried out, for example, amino acid in which the amino group is protected (for example, amino acid of the formula Q¹—AA¹—OH, Q²—AA²—OH, Q^(n)—AA^(n)—OH etc.) is reacted with an acid halide (pivaloyl chloride, tosyl chloride, mesyl chloride etc.) or an acid derivative (ethyl chloroformate, isobutyl chloroformate etc.) in an inert organic solvent (chloroform, methylene chloride, diethyl ether, THF etc.) or without solvents, in the presence of tertiary amine (pyridine, triethylamine, dimethylaniline or dimethylaminopyridine etc.) at 0˜40° C. to give mixed acid anhydride. The obtained mixed acid anhydride and an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H or a (poly)peptide prepared by coupling of the corresponding compound and then by removing an amino-protective group (for example, a (poly)peptide of the formula H—EE—Z or the formula

etc.) are reacted in an inert organic solvent (chloroform, methylene chloride, diethylether, THF etc.) at 0˜70° C.

(3) method using condensing agent such as EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimido), PyBrop (bromo-tris-pyrolydino-phosphoniumuhexafluorophosphate), DCC (dicyclohexyl-carbodiimido) etc. may be carried out, for example; amino acid in which an amino group is protected (for example, amino acid of the formula Q¹—AA¹—OH, Q²—AA²—OH, Q^(n)—AA^(n)—OH etc.) and an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H or a (poly)peptide prepared by coupling of the corresponding compound and then by removing an amino-protective group (for example, a (poly)peptide of the formula H—EE—Z or the formula

etc.) are reacted in an inert organic solvent (chloroform, methylene chloride, diethylether or THF etc.) or without solvents in the presence or absence of tertiary amine (pyridine, triethylamine, dimethylaniline, dimethylaminopyridine, diisopropylethylamine etc.) using EDC, PyBrop or DCC etc. at 0˜40° C.

Preferably, these reactions (1), (2) and (3) described above are carried out under an atmosphere of inert gas (argon, nitrogen, etc.) on anhydrous condition.

Removal of a protective group may be carried out by the known method. For example, removal of CBZ or Bzl may be carried out under the atmosphere of hydrogen gas, in an organic solvent (methanol, ethanol or THF etc.) by using catalyst (Pd—C, Pd or Ni etc.) at 0˜50° C. Removal of Boc may be carried out in a water-miscible organic solvent (methanol, ethanol, THF or dioxane etc.) by using organic acid (acetic acid, p-toluene sulfonic acid, trifluoro acetic acid or trichloro acetic acid etc.) or inorganic acid (hydrochloric acid or hydrobromic acid etc.) at 0˜90° C. Removal of both Boc and Bzl at the same time may be carried out in the presence of thioanisole, m-chlezole etc. in trifloromethane sulfonic acid+trifluoro acetic acid or hydrogen fluoride.

In each reaction in the present specification, obtained products may be purified by conventional techniques. For example, purification may be carried out by distillation at atmospheric or reduced pressure, by high performance liquid chromatography, by thin layer chromatography or by column chromatography using silica gel or magnesium silicate, by washing or by recrystallization. Purification may be carried out after each reaction, or after a series of reactions.

A peptide of the formula (I) may be converted into a corresponding acid addition salt thereof by the known method.

Starting Materials and Reagents

The starting materials and reagents in the present invention are known or may be prepared by known methods.

The Method for Assay

The enzymatic reaction used in the method for assaying of the present invention is shown in Reaction scheme 3.

(in Reaction scheme 3, all the symbols are as defined hereinbefore.)

As for a sample, in case of body fluid except for gastric juice such as blood, urine etc., human pepsinogen II is activated to human pepsin II in the First reaction, and the obtained human pepsin II recognizes and digests a peptide of the formula (I) (wherein all the symbols are as defined hereinbefore.) or an acid addition salt thereof as a substrate, specifically. This activation of human pepsinogen II may be carried out, for example, under an acidic condition in combination with digesting a substrate at the same time or separately. As for this acidic condition, pH1.0˜6.0 is preferable. A buffer includes tartaric acid, glycine, citric acid, oxalic acid, formic acid or and acetic acid buffer preferably. An amino acid derivative of the formula (II)

(wherein all the symbols are as defined hereinbefore.) which is released after digesting reaction is digested by aminopeptidase (for example, aminopeptidase M derived from pig kidney) at pH6˜9 in Second reaction to release an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H. It is possible to assay human pepsinogen II in a sample by detecting the obtained aniline, aminocoumarine or aminonaphthalene derivative.

On the other hand, in case of gastric juice, human pepsin II recognizes and digests a peptide of the formula (I) (wherein all the symbols are as defined hereinbefore.) or an acid addition salt thereof as a substrate under an acidic condition in First reaction specifically. As for this acidic condition, pH1.5˜6.0 is preferable. A buffer includes tartaric acid, glycine, citric acid, oxalic acid, formic acid, or acetic acid buffer preferably. An amino acid derivative of the formula (II) which is released after digesting reaction is digested similarly to give an aniline, aminocoumarine or aminonaphthalene derivative. It is possible to assay human pepsin II in a sample by detecting the obtained aniline, aminocoumarine or aminonaphthalene derivative.

The detecting an aniline derivative may be carried out by the assaying the increase in absorbance of aniline derivative itself or by the assaying corresponding adequate coloring agent. An aniline derivative may be converted into a corresponding adequate coloring agent by reacting the said aniline derivative under an acidic condition to give diazo chromophore. The concrete material for diazo-coupling includes, 3,5-xylenol, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethylaniline or its salt (MAOS) etc. Such a converting may be carried out by addition of metal kilate complex such as pentacyanoamine feroate etc., by oxidizing and condensing a phenol derivative, aniline derivative such as N-ethyl-N-(3-sulfopropyl)-3-methoxyaniline (ADPS) etc. or xylenol derivative etc. and NalO₄ or by oxidizing and condensing with using oxidase such as bilirubin oxidase, polyphenol oxidase or ascorbic acid oxidase.

The detecting an aminocoumarine derivative, aminonaphthalene derivative is carried out by fluorometery (for example, λex=380 nm, λem=460 nm on 7-amino-4-methylcoumarin; λex=335 nm, λem=410 nm on 4-methyl-2-aminonaphthalene).

INDUSTRIAL AVAILABILITY

A peptide of the formula (i) or an acid addition salt thereof of the present invention is a substrate possessing the specificity for human pepsin II and high sensitivity (digesting a substrate by pepsin II at a high rate and/or being able to produce efficient coloring). Therefore, a method for assaying human pepsin II or human pepsinogen II by using a peptide or an acid addition salt thereof of the present invention is useful for diagnosis of gastric diseases such as gastric cancer, gastric ulcer etc. and contributes to the clinical field.

BEST MODE TO CARRY OUT THE INVENTION

The following examples are intended to illustrate, but not limit, the present invention. The solvents in parentheses of NMR show solvents used in determination. The meaning of abbreviation is as follows:

2-Naph=2-naphthyl,

p-NA=p-nitroaniline,

Boc=tert-butoxycarbonyl,

OxR=oxymresin,

Bop=Bop reagent: benzotriazole-1-yloxytris(dimethylamino)-phosphoniumhexafluorophosphate,

DMF=N, N-dimethylformamide,

DIPEA=diisopropylethylamine,

Bzl=benzyl,

TFA=trifluoroacetic acid,

TFMSA=trifluoromethansulphonic acid.

EXAMPLE 1 Synthesis of the Peptide of the Formula ProLeuSerGluAla(2-Naph)Ala-pNA (SEQ ID NO:f1)

1(1): Forming Solid Phase to Connect Resin (BocAla(2-Naph)-OxR)

Oxymresin (100 mg) was put into polystyrene column and swelled by addition of dichloromethan (1.0 ml) thereto. To a solution of butanol (1 M) and Bop in DMF (1 M) (150 μl), a solution of BocAla(2-Naph)—OH in DMF (1 M) (150 μl) was added. DIPEA (43 μl) was added thereto at 0° C. The mixture was stirred and added to the said polystyrene column. After stirring the mixture for 18 hours, the reaction mixture was stirred, filtered and washed with DMF three times and toluene three times successively to give BocAla(2-Naph)-OxR. The obtained compound was used in the next reaction without purification.

1(2): Lengthening Amino Acid Chain

(BocProLeuSer(Bzl)Glu (Bzl)Ala(2-Naph)-OxR)

Into BocAla(2-Naph)-OxR (prepared in Example 1(1).) in polystyrene column, a solution of 20%TFA/toluene (3 ml) was added. After stirring the mixture for 2 hours, the reaction mixture was stirred, filtered and washed with toluene two times, isopropanol one time and DMF three times successively. To a solution of butanol (1 M) and Bop in DMF (1 M) (150 μl), a solution of BocGlu(Bzl)—OH in DMF (1 M) (150 μl) was added. DIPEA (43 μl) was added thereto at 0° C. The solution was stirred and added to the said polystyrene column. After stirring the mixture for 20 hours, the reaction mixture was stirred, filtered and washed with DMF three times and toluene three times successively to obtain BocGlu(Bzl)Ala(2-Naph)-OxR.

By the same procedure as above, the obtained compound was reacted to condense with Ser(Bzl), Leu and Pro successively to give BocProLeuSer(Bzl)Glu(Bzl)Ala(2-Naph)-OxR. The obtained compound was used in the next reaction without purification

1(3): Separation of Amino Acid from Resin

To BocProLeuSer(Bzl)Glu(Bzl)Ala(2-Naph)-OxR (prepared in Example 1(2).), a solution of AlapNA·HCl (0.25 M), DIPEA (0.25 M) and acetic acid in DMF (0.25 M) (1000 μl) was added. The mixture was stirred for 24 hours and extracted with DMF three times. The extract was distilled off under reduced pressure, distilled water (10 ml) was added thereto. The mixture was stirred and filtered. The residue was washed with distilled water. The residue was dissolved into acetonitlile (20 ml). Toluene (10 ml) was added thereto. The mixture was dried under reduced pressure. The obtained crude was dissolved into TFA (4 ml). m-Cresol (200 μl) and TFMSA (80 ml) were added thereto at 0° C. The mixture was stirred for 2 hours. TFA was distilled off under reduced pressure. The residue was added dropwise to diethyl ether (300 ml) with stirring at 0° C. The precipitate was separated with centrifugation. The obtained precipitate was washed with iced ether (10 ml) three times, dried under reduced pressure. The obtained crude was dissolved into 30% acetonitolile and purified with C18-HPLC-column to give the title compound (20.3 mg) having the following physical data.

MS: (M+H)m/z=833; NMR: (CD₃OD) δ=8.18 (2H, d), 7.81 (2H, d), 7.78-7.70 (4H, M), 7.41-7.37 (3H, M), 4.77 (1H, dd), 4.50-4.26 (5H, M), 3.86 (1H, dd), 3.75 (1H, dd), 3.39 (2H, dd), 3.12 (2H, dd), 2.48-2.37 (1H, M), 2.25 (2H, t), 2.16-2.08 (1H, M), 2.07-1.94 (4H, M), 1.88-1.60 (5H, M), 1.45 (3H, d), 0.97-0.92 (6H, M).

EXAMPLES 2(1)˜2(83)

By the same procedure as Example 1 with using various kinds of amino acid and amino acid derivatives of the formula (II-A)

(in which Z^(a) is an aniline derivative residue and the other symbols are as defined hereinbefore.), the peptides of the formula (I-B) having the following physical data were obtained. The results are shown in Table 2 (Tables 2-1˜2-6).

TABLE 2 Definition of each symbol Example No. Q

R⁴ (EE)m Z Salt SEQ ID NO: MALDI positive     m/z     (M +  (M +  (M +  H)+  Na)+   K)+ 2(1) Leu Ser 4-I-Phenyl H single bond p-NA TFA SEQ ID NO:2 669 691 2(2) Pro Gln Gln Ala 2-Naphthyl H single bond p-NA TFA SEQ ID NO:3 817 839 855 2(3) Pro Gln Gln Ala 4-I-Phenyl H single bond p-NA TFA SEQ ID NO:4 893 915 931 2(4) Pro Gln Gln Ala 4-Cl-Phenyl H single bond p-NA TFA SEQ ID NO:5 801 823 839 2(5) Pro Gln Gln Ala 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:6 831 853 869 2(6) Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:7 907 929 945 2(7) Pro Gln Gln Ala 4-Cl-Phenyl Me single bond p-NA TFA SEQ ID NO:8 815 837 853 2(8) Pro Gln Gln Ala 2-Naphthyl Et single bond p-NA TFA SEQ ID NO:9 845 867 883 2(9) Pro Gln Gln Ala 4-I-Phenyl Et single bond p-NA TFA SEQ ID NO:10 921 943 2(10) Pro Gln Gln Ala 4-Cl-Phenyl Et single bond p-NA TFA SEQ ID NO:11 829 851 2(11) Pro Gln Gln Ala 2-Naphthyl n-Pr single bond p-NA TFA SEQ ID NO:12 859 881 897 2(12) Pro Gln Gln Ala 4-I-Phenyl n-Pr single bond p-NA TFA SEQ ID NO:13 935 957 973 2(13) Pro Gln Gln Ala 4-Cl-Phenyl n-Pr single bond p-NA TFA SEQ ID NO:14 843 865 881 2(14) Ac Lys Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:15 1077 1099 1115 2(15) Leu Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:16 1020 1042 1058 2(16) Asn Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:17 1021 1043 2(17) Gln Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:18 1035 1057 1073 2(18) Ala Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:19 978 1000 1016 2(19) Val Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:20 1006 1028 1044 2(20) Gly Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:21 964 986 1002 2(21) Phe Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:22 1054 1076 1092 2(22) Pro Gln Gln Asn 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:23 874 2(23) Pro Gln Gln Gln 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:24 888 910 926 2(24) Pro Gln Gln Gly 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:25 817 839 855 2(25) Pro Gln Gln Met 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:26 891 2(26) Pro Gln Gln Ser 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:27 847 869 2(27) Pro Gln Gln Asp 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:28 875 897 913 2(28) Pro Gln Gln Glu 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:29 889 911 2(29) Pro Gln Asn Glu 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:30 875 897 2(30) Pro Gln Ala Glu 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:31 832 2(31) Pro Gln Gly Glu 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:32 818 2(32) Pro Gln Leu Glu 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:33 874 896 2(33) Pro Gln Glu Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:34 890 912 928 2(34) Pro Gln Asp Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:35 876 898 2(35) Pro Gln Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:36 848 870 886 2(36) Pro Asn Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:37 834 856 2(37) Pro Ala Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:38 791 813 2(38) Pro Val Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:39 819 841 2(39) Pro Met Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:40 851 873 889 2(40) Pro Ile Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:41 833 855 2(41) Pro Gly Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:42 777 799 2(42) Pro Glu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:43 849 871 887 2(43) Pro Asp Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:44 835 2(44) Pro Ser Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:45 807 829 845 2(45) Pro Thr Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:46 821 843 859 2(46) Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:47 850 872 888 2(47) Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:48 807 829 845 2(48) Val Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:49 835 857 873 2(49) Met Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:50 867 889 905 2(50) Ile Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:51 849 871 887 2(51) Gly Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:52 793 815 831 2(52) Leu Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:53 849 871 887 2(53) Gln Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:54 864 2(54) Lys Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:55 864 886 902 2(55) Glu Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:56 865 887 903 2(56) Ser Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:57 823 845 861 2(57) Thr Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:58 837 859 875 2(58) Tyr Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:59 899 921 937 2(59) Ac Lys Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:60 906 928 944 2(60) Pro Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:61 947 969 2(61) Ac Lys Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:62 1020 1042 1058 2(62) Pro Ser Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:63 1034 1056 2(63) Pro Asn Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:64 1061 2(64) Pro Gly Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:65 1004 1026 1042 2(65) Ac Lys Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:66 977 999 2(66) β-Ala Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:67 921 943 959 2(67) Sar Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:68 943 2(68) Me-Val Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:69 849 871 887 2(69) Me-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:70 821 843 2(70) Sar Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:71 807 829 2(71) Pro Leu Ser Glu 4-Cl-Phenyl Me single bond p-NA TFMSA SEQ ID NO:72 817 839 855 2(72) Pro Leu Ser Glu 3,4-DCP Me single bond p-NA TFMSA SEQ ID NO:73 851 873 2(73) Val Leu Ser Glu 4-Cl-Phenyl Me single bond p-NA TFMSA SEQ ID NO:74 819 841 2(74) D-Ala Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:75 921 943 2(75) D-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:76 807 829 845 2(76) β-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:77 807 829 845 2(77) γ-Abu Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:78 821 843 859 2(78) Leu Ser Glu 2-Naphthyl Me Leu p-NA TFMSA SEQ ID NO:79 871 887 2(79) Leu Ser Glu 2-Naphthyl Me Ala p-NA TFMSA SEQ ID NO:80 807 829 845 2(80) Leu Ser Glu 2-Naphthyl Me Gly p-NA TFMSA SEQ ID NO:81 793 815 831 2(81) Sar Leu Ser Glu 2-Naphthyl Me Ala p-NA TFMSA SEQ ID NO:82 878 900 916 2(82) Sar Leu Ser Glu 2-Naphthyl Me Gly p-NA TFMSA SEQ ID NO:83 864 886 902 2(83) Sar Leu Ser Glu 2-Naphthyl Me Ala m-ASD TFMSA SEQ ID NO:84 863 885 901 2(84) Sar Ser Gly 2-Naphthyl Me Ala DCHA TFMSA SEQ ID NO:85 732 754 770

(In Table 2, various symbols are as defined hereinbefore.)

EXAMPLES 3 Assaying Pepsin I and II on Digesting the Substrate of the Present Invention Reagent

Tartaric acid buffer or glycine buffer (pH2.0) containing each peptide (0.5 mM) prepared in Examples 1 and 2(3) etc. (Examples in Table 3 described hereinafter).

Enzyme Solution I

An aqueous solution of human pepsin I or human pepsin II (0.01 mg/ml)

Method for Assay

(1) Assay by HPLC

Enzyme solution I (0.1 ml) was added to Reagent (1.0 ml). After incubation of the mixture at 37° C. for 10, 30, 60 minutes, the mixture solution (0.3 ml) was collected. To the collected solution, 2N-NaOH (0.025 ml) was added to terminate the reaction. After addition of 2N-HCl (0.025 ml) to the mixture, protein was removed by the ultrafiltration. The assaying the amino acid derivatives of the formula (II-A)

(in which all the symbols are as defined hereinbefore.)

which was released after digesting by human pepsin in the obtained solution was carried out by HPLC using C18 column. The ratio of digesting rate of pepsin II/pepsin I was calculated according to the result from assay by HPLC. Such assay is carried out to confirm that a substrate was digested by pepsin I or pepsin II correctly and that the amino acid derivatives of the formula (II-A) were released. The results are shown in Table 3 (Tables 3-1˜3-3).

TABLE 3

Definition of symbol Exam- ple No. Q

R⁴ (EE)m Z salt SEQ ID NO: pepsin II digesting rate μM/min · 1 μg Enz pepsin I digesting rate μM/min · 1 μg Enz ration of digesting rate (pepsin II/ pepsin I) 1 Pro Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:1 55.40 0.2795 198.2 2(3) Pro Gln Gln Ala 4-I-Phenyl H single bond p NA TFA SEQ ID NO:4 4.23 0.0020 2065.1 2(7) Pro Gln Gln Ala 4-Cl-Phenyl Me single bond p-NA TFA SEQ ID NO:8 3.50 0.0335 104.4 2(11) Pro Gln Gln Ala 2-Naphthyl n-Pr single bond p-NA TFA SEQ ID NO:12 4.10 0.0235 174.9 2(14) Ac Lys Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:15 3.85 0.0094 410.2 2(16) Asn Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:17 8.95 0.0082 1094.8 2(18) Ala Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA TFA SEQ ID NO:19 9.20 0.0122 757.0 2(22) Pro Gln Gln Asn 2-Naphthyl Me single bond p-NA TEA SEQ ID NO:23 12.87 0.0578 222.6 2(23) Pro Gln Gln Gln 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:24 5.90 0.0191 308.8 2(24) Pro Gln Gln Gly 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:25 12.06 0.0058 2081.6 2(25) Pro Gln Gln Met 2-Naphthyl Me single bond p-NA TFA SEQ ID NO:26 5.56 0.0063 889.7 2(33) Pro Gln Glu Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:34 25.41 0.0632 402.3 2(34) Pro Gln Asp Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:35 15.40 0.0216 711.9 2(36) Pro Asn Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:37 21.22 0.1096 193.5 2(39) Pro Met Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:40 45.79 0.2277 201.1 2(45) Pro Thr Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:46 40.55 0.2512 161.4 2(51) Gly Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:52 54.43 0.1631 333.8 2(53) Gln Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:54 61.96 0.0998 621.0 2(54) Lys Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:55 48.39 0.2739 176.7 2(56) Ser Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:57 10.94 0.0194 562.6 2(57) Thr Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:58 18.78 0.0284 660.9 2(61) Ac Lys Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:62 36.81 0.1681 219.0 2(63) Pro Asn Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:64 29.84 0.1763 169.2 2(69) Me-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:70 73.08 0.9851 74.2 2(70) Sar Leu Ser Glu 2-Naphthyl Me single bond p-NA TFMSA SEQ ID NO:71 49.56 0.3128 158.4 2(78) Leu Ser Glu 2-Naphthyl Me Leu p-NA TFMSA SEQ ID NO:79 54.41 2.6240 20.74 2(80) Leu Ser Glu 2-Naphthyl Me Gly p-NA TFMSA SEQ ID NO:81 15.77 0.1500 105.48 2(83) Sar Leu Ser Glu 2-Naphthyl Me Ala m-ASD TFMSA SEQ ID NO:84 70.66 2.3660 29.87 2(84) Sar Ser Gly 2-Naphthyl Me Ala DCHA TFMSA SEQ ID NO:85 33.07 0.2767 119.5

(In Table 3, all the symbols are as defined hereinbefore.)

As is shown clearly from the above Table, we understand that a peptide of the present invention has the specificity for pepsin II.

EXAMPLE 4 Assaying Human Pepsinogen II by the Method of the Present Invention (Calibration Curve) Reagent Solution I

Nα-Me-GlyLeuSerGluAla(2-Naph)Ala-pNA.TFMSA (SEQ ID NO:71)(prepared in Example 2(70).) was dissolved into tartaric acid buffer (50 mM, pH2.0) to be at concentration of 0.5 mM.

Reagent Solution II

Aminopeptidase (marketed from Sigma Co.) was dissolved into Tris-HCl buffer (1.0 M, pH8.5) to be at concentration of 3.4 U/ml.

Sample

Purified human pepsinogen II

Method for Assay

Reagent solution I (0.25 ml) was added to sample (0.025 ml). After incubation of the mixture at 37° C. for 5 minutes, Reagent solution II (0.05 ml) was added thereto. After incubation of the mixture at 37° C. for 5 minutes, the increase in absorbance (Es) at 405 nm with reference at 480 nm was determined. On the other hand, reagent blank value (E(BL)) was determined by the same procedure as above using saline. According to the following, the increase in absorbance for 5 minutes (E) was calculated.

E=Es−E(BL)

The correlation between the concentration of pepsinogen II and increase in absorbance is shown in FIG. 1.

As is shown clearly from FIG. 1, calibration curve obtained from each pepsinogen II level (ng/ml) and the plotted increase in absorbance passes through zero point showing a good linearity and quantatativeness.

EXAMPLES 5 Assaying Human Pepsinogen II in Blood by the Method of the Present Invention (The Correlation of the Method Between the Present Invention and RIA) Reagent Solutions I and II

Same solutions as Example 4.

Sample

52 Samples of human serum

Method for Assay

By the same procedure as Example 4, the increase in absorbance for 5 minutes (E) was calculated.

Comparison

The assaying serum pepsinogen II was carried out by a marketed kit for assaying pepsinogen II (Dinabott Co) (RIA method) according to the procedure described in explanation. The correlation of the results of the method between the present invention and RIA is shown in FIG. 2.

As is shown clearly from FIG. 2, we understand that there is a good correlation of the results of the method between the present invention and RIA, and that serum pepsinogen II was determined correctly by the method of the present invention.

EXAMPLE 6 Assaying Human Pepsinogen II by the Method of the Present Invention Reagent Solution III

Nα-Me-GlySerGlyAla(2-Naph)AlaAla-DCHA.TFMSA (SEQ ID NO:85)(prepared in Example 2(84).) and N-ethyl-N-(3-sulphopropyl)-3-methyoxyaniline sodium salt.monohydrate (marketed from Dojin Chemical Research Institute Co.) were dissolved into citrate buffer (50 mM, pH2.0) to be at the concentration of 0.36 mM and 40 mM, respectively.

Reagent Solution IV

Aminopeptidase M (marketed from Beringer Co.) and polyphenoloxidase (marketed from Takara-shuzo) were dissolved into Tris-HCl buffer (2.0 M, pH8.33) to be at concentration of 0.67 U/ml and 0.2 U/ml, respectively.

Sample

Purified human pepsinogen II

Method for Assay

Reagent solution III (0.25 ml) was added to sample (0.025 ml). After incubation of the mixture at 37° C. for 5 minutes, Reagent solution IV (0.05 ml) was added thereto. After incubation of the mixture at 37° C. for 5 minutes, the increase in absorbance (Es) at 700 nm with reference at 800 nm was determined. On the other hand, reagent blank value (E(BL)) was determined by the same procedure as above using saline. The increase in absorbance for 5 minutes (E) was calculated by the same procedure as Example 4.

The correlation between the concentration of pepsinogen II and increase in absorbance is shown in FIG. 3.

As is shown clearly from FIG. 3, calibration curve obtained from each pepsinogen II level (ng/ml) and the plotted increase in absorbance passes through zero point showing a good linearity and quantatativeness.

EXAMPLES 7 Assaying Human Pepsinogen II by the Method of the Present Invention (The Correlation of the Method Between the Present Invention and RIA) Reagent Solutions III and IV

Same solution as Example 6.

Sample

52 Samples of human serum

Method for Assay

By the same procedure as Example 6, the increase in absorbance for 5 minutes (E) was calculated.

Comparison

The assaying serum pepsinogen II was carried out by the same procedure as Example 5. The correlation of the results of the method between the present invention and RIA is shown in FIG. 4.

As is shown clearly from FIG. 4, we understand that there is a good correlation of the results of the method between the present invention and RIA, and that serum pepsinogen II was determined correctly by the method of the present invention.

92 1 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 1 Pro Leu Ser Glu Xaa Xaa 1 5 2 4 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 2 Leu Ser Xaa Xaa 1 3 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 3 Pro Gln Gln Ala Xaa Xaa 1 5 4 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 4 Pro Gln Gln Ala Xaa Xaa 1 5 5 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 5 Pro Gln Gln Ala Xaa Xaa 1 5 6 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 6 Pro Gln Gln Ala Xaa Xaa 1 5 7 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 7 Pro Gln Gln Ala Xaa Xaa 1 5 8 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 8 Pro Gln Gln Ala Xaa Xaa 1 5 9 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 9 Pro Gln Gln Ala Xaa Xaa 1 5 10 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 10 Pro Gln Gln Ala Xaa Xaa 1 5 11 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 11 Pro Gln Gln Ala Xaa Xaa 1 5 12 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 12 Pro Gln Gln Ala Xaa Xaa 1 5 13 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 13 Pro Gln Gln Ala Xaa Xaa 1 5 14 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 14 Pro Gln Gln Ala Xaa Xaa 1 5 15 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 15 Lys Pro Gln Gln Ala Xaa Xaa 1 5 16 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 16 Leu Pro Gln Gln Ala Xaa Xaa 1 5 17 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 17 Asn Pro Gln Gln Ala Xaa Xaa 1 5 18 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 18 Gln Pro Gln Gln Ala Xaa Xaa 1 5 19 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 19 Ala Pro Gln Gln Ala Xaa Xaa 1 5 20 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 20 Val Pro Gln Gln Ala Xaa Xaa 1 5 21 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 21 Gly Pro Gln Gln Ala Xaa Xaa 1 5 22 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 22 Phe Pro Gln Gln Ala Xaa Xaa 1 5 23 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 23 Pro Gln Gln Asn Xaa Xaa 1 5 24 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 24 Pro Gln Gln Gln Xaa Xaa 1 5 25 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 25 Pro Gln Gln Gly Xaa Xaa 1 5 26 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 26 Pro Gln Gln Met Xaa Xaa 1 5 27 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 27 Pro Gln Gln Ser Xaa Xaa 1 5 28 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 28 Pro Gln Gln Asp Xaa Xaa 1 5 29 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 29 Pro Gln Gln Glu Xaa Xaa 1 5 30 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 30 Pro Gln Asn Glu Xaa Xaa 1 5 31 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 31 Pro Gln Ala Glu Xaa Xaa 1 5 32 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 32 Pro Gln Gly Glu Xaa Xaa 1 5 33 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 33 Pro Gln Leu Glu Xaa Xaa 1 5 34 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 34 Pro Gln Glu Glu Xaa Xaa 1 5 35 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 35 Pro Gln Asp Glu Xaa Xaa 1 5 36 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 36 Pro Gln Ser Glu Xaa Xaa 1 5 37 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 37 Pro Asn Ser Glu Xaa Xaa 1 5 38 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 38 Pro Ala Ser Glu Xaa Xaa 1 5 39 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 39 Pro Val Ser Glu Xaa Xaa 1 5 40 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 40 Pro Met Ser Glu Xaa Xaa 1 5 41 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 41 Pro Ile Ser Glu Xaa Xaa 1 5 42 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 42 Pro Gly Ser Glu Xaa Xaa 1 5 43 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 43 Pro Glu Ser Glu Xaa Xaa 1 5 44 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 44 Pro Asp Ser Glu Xaa Xaa 1 5 45 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 45 Pro Ser Ser Glu Xaa Xaa 1 5 46 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 46 Pro Thr Ser Glu Xaa Xaa 1 5 47 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 47 Asn Leu Ser Glu Xaa Xaa 1 5 48 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 48 Ala Leu Ser Glu Xaa Xaa 1 5 49 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 49 Val Leu Ser Glu Xaa Xaa 1 5 50 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 50 Met Leu Ser Glu Xaa Xaa 1 5 51 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 51 Ile Leu Ser Glu Xaa Xaa 1 5 52 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 52 Gly Leu Ser Glu Xaa Xaa 1 5 53 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 53 Leu Leu Ser Glu Xaa Xaa 1 5 54 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 54 Gln Leu Ser Glu Xaa Xaa 1 5 55 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 55 Lys Leu Ser Glu Xaa Xaa 1 5 56 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 56 Glu Leu Ser Glu Xaa Xaa 1 5 57 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 57 Ser Leu Ser Glu Xaa Xaa 1 5 58 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 58 Thr Leu Ser Glu Xaa Xaa 1 5 59 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 59 Tyr Leu Ser Glu Xaa Xaa 1 5 60 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 60 Lys Leu Ser Glu Xaa Xaa 1 5 61 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 61 Pro Asn Leu Ser Glu Xaa Xaa 1 5 62 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 62 Lys Asn Leu Ser Glu Xaa Xaa 1 5 63 8 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 63 Pro Ser Asn Leu Ser Glu Xaa Xaa 1 5 64 8 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 64 Pro Asn Asn Leu Ser Glu Xaa Xaa 1 5 65 8 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 65 Pro Gly Asn Leu Ser Glu Xaa Xaa 1 5 66 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 66 Lys Ala Leu Ser Glu Xaa Xaa 1 5 67 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 67 Ala Asn Leu Ser Glu Xaa Xaa 1 5 68 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 68 Gly Asn Leu Ser Glu Xaa Xaa 1 5 69 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 69 Val Leu Ser Glu Xaa Xaa 1 5 70 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 70 Xaa Leu Ser Glu Xaa Xaa 1 5 71 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 71 Gly Leu Ser Glu Xaa Xaa 1 5 72 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 72 Pro Leu Ser Glu Xaa Xaa 1 5 73 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 73 Pro Leu Ser Glu Xaa Xaa 1 5 74 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 74 Val Leu Ser Glu Xaa Xaa 1 5 75 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 75 Ala Asn Leu Ser Glu Xaa Xaa 1 5 76 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 76 Ala Leu Ser Glu Xaa Xaa 1 5 77 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 77 Ala Leu Ser Glu Xaa Xaa 1 5 78 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 78 Xaa Leu Ser Glu Xaa Xaa 1 5 79 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 79 Leu Ser Glu Xaa Ala Xaa 1 5 80 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 80 Leu Ser Glu Xaa Ala Xaa 1 5 81 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 81 Leu Ser Glu Xaa Ala Xaa 1 5 82 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 82 Gly Leu Ser Glu Xaa Ala Xaa 1 5 83 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 83 Gly Leu Ser Glu Xaa Ala Xaa 1 5 84 7 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 84 Gly Leu Ser Glu Xaa Ala Xaa 1 5 85 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 85 Gly Ser Gly Xaa Ala Xaa 1 5 86 8 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 86 Lys Pro Ala Ala Phe Xaa Arg Leu 1 5 87 8 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 87 Lys Pro Val Val Phe Xaa Arg Leu 1 5 88 4 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 88 Xaa Xaa Phe Xaa 1 89 4 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 89 Xaa His Phe Xaa 1 90 4 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 90 Xaa His Phe Xaa 1 91 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 91 Xaa Ala Phe Phe Ala Xaa 1 5 92 6 PRT Artificial Sequence substrate for human pepsin II or pepsinogen II 92 Xaa Ala Phe Phe Ala Xaa 1 5 

What is claimed is:
 1. A peptide of the formula (I)

wherein, Q is Q^(a)—(AA)n—, wherein AA is L-amino acid, n is 0 or an integer of 1-15, Q^(a) is hydrogen, C1-4 alkyl, an amino-protective group, D- or L-amino acid residue or NH₂—(CH₂)r—CO—, where r is an integer of 2-7, R¹ and R² are (i) hydrogen or halogen or, (ii) R¹, R² and an unsaturated bond together form an aromatic carbon ring that may be substituted by halogen, R³ is hydrogen or halogen, R⁴ is hydrogen, C1-3 alkyl or hydroxymethyl, EE is D- or L-amino acid, m is 0 or 1, and Z is an aniline derivative residue, an aminocoumarine derivative residue or an aminonaphthalene derivative residue, with the proviso that (I) when n is 2 or more, each AA is same or different, and that (2) the compounds wherein all of R¹, R² and R³ are hydrogen are excluded, or an acid addition salt thereof.
 2. A peptide according to claim 1 in which m is
 0. 3. A peptide according to claim 1 in which m is
 1. 4. A peptide according to claims 1 to 3 in which Q is Q^(b)—(AA)s—A¹— wherein, A¹ is Gly, Ala, Ser, Asp, Glu, Asn, Gln or Met, s is an integer of 2, 3, 4 or 5, Q^(b) is hydrogen, C1-4 alkyl, C 1-6 alkylcarbonyl, D- or L-amino acid or NH₂—(CH₂)r—CO—, where r is as defined in claim 1, and each AA is as defined in claim
 1. 5. A peptide according to claims 1 to 3 in which Q is Q^(b)—(AA)t—A²—A¹¹— wherein A¹¹ is Gly, Ala, Glu or Asn, A² is Gly, Ala, Leu, Ser, Asp, Glu, Asn or Gln, t is an integer of1, 2, 3 or 4, Q^(b) is hydrogen, C1-4 alkyl, C1-6 alkylcarbonyl, D- or L-amino acid or NH₂—(CH₂)r—CO—, where r is as defined in claim 1, and each AA is as defined in claim
 1. 6. A peptide according to claims 1 to 3 in which Q is Q^(b)—(AA)t—A²²—A¹¹— wherein A¹¹ is Gly, Ala, Glu or Asn, A²² is Gly, Ser, Glu or Gln, t is an integer of1, 2, 3or 4, Q^(b) is hydrogen, C1-4 alkyl, C 1-6 alkylcarbonyl, D- or L-amino acid or NH₂—(CH₂)r—CO— where r is as defined in claim 1, and each AA is as defined in claim
 1. 7. A peptide of the formula (I-A):

wherein, each symbol is as defined in Table 1 (Tables 1-1˜1-4): TABLE 1 Definition of each symbol No. Q

R⁴ (EE)m Z SEQ ID NO: (1) Pro Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:1 (2) Leu Ser 4-I-Phenyl H single bond p-NA SEQ ID NO:2 (3) Pro Gln Gln Ala 2-Naphthyl H single bond p-NA SEQ ID NO:3 (4) Pro Gln Gln Ala 4-I-Phenyl H single bond p-NA SEQ ID NO:4 (5) Pro Gln Gln Ala 4-Cl-Phenyl H single bond p-NA SEQ ID NO:5 (6) Pro Gln Gln Ala 2-Naphthyl Me single bond p-NA SEQ ID NO:6 (7) Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:7 (8) Pro Gln Gln Ala 4-Cl-Phenyl Me single bond p-NA SEQ ID NO:8 (9) Pro Gln Gln Ala 2-Naphthyl Et single bond p-NA SEQ ID NO:9 (10) Pro Gln Gln Ala 4-I-Phenyl Et single bond p-NA SEQ ID NO:10 (11) Pro Gln Gln Ala 4-Cl-Phenyl Et single bond p-NA SEQ ID NO:11 (12) Pro Gln Gln Ala 2-Naphthyl n-Pr single bond p-NA SEQ ID NO:12 (13) Pro Gln Gln Ala 4-I-Phenyl n-Pr single bond p-NA SEQ ID NO:13 (14) Pro Gln Gln Ala 4-Cl-Phenyl n-Pr single bond p-NA SEQ ID NO:14 (15) Ac Lys Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:15 (16) Leu Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:16 (17) Asn Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:17 (18) Gln Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:18 (19) Ala Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:19 (20) Val Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:20 (21) Gly Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:21 (22) Phe Pro Gln Gln Ala 4-I-Phenyl Me single bond p-NA SEQ ID NO:22 (23) Pro Gln Gln Asn 2-Naphthyl Me single bond p-NA SEQ ID NO:23 (24) Pro Gln Gln Gln 2-Naphthyl Me single bond p-NA SEQ ID NO:24 (25) Pro Gln Gln Gly 2-Naphthyl Me single bond p-NA SEQ ID NO:25 (26) Pro Gln Gln Met 2-Naphthyl Me single bond p-NA SEQ ID NO:26 (27) Pro Gln Gln Ser 2-Naphthyl Me single bond p-NA SEQ ID NO:27 (28) Pro Gln Gln Asp 2-Naphthyl Me single bond p-NA SEQ ID NO:28 (29) Pro Gln Gln Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:29 (30) Pro Gln Asn Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:30 (31) Pro Gln Ala Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:31 (32) Pro Gln Gly Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:32 (33) Pro Gln Leu Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:33 (34) Pro Gln Glu Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:34 (35) Pro Gln Asp Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:35 (36) Pro Gln Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:36 (37) Pro Asn Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:37 (38) Pro Ala Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:38 (39) Pro Val Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:39 (40) Pro Met Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:40 (41) Pro Ile Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:41 (42) Pro Gly Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:42 (43) Pro Glu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:43 (44) Pro Asp Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:44 (45) Pro Ser Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:45 (46) Pro Thr Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:46 (47) Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:47 (48) Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:48 (49) Val Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:49 (50) Met Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:50 (51) Ile Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:51 (52) Gly Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:52 (53) Leu Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:53 (54) Gln Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:54 (55) Lys Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:55 (56) Glu Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:56 (57) Ser Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:57 (58) Thr Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:58 (59) Tyr Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:59 (60) Ac Lys Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:60 (61) Pro Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:61 (62) Ac Lys Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:62 (63) Pro Ser Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:63 (64) Pro Asn Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:64 (65) Pro Gly Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:65 (66) Ac Lys Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:66 (67) β-Ala Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:67 (68) Sar Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:68 (69) Me-Val Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:69 (70) Me-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:70 (71) Sar Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:71 (72) Pro Leu Ser Glu 4-Cl-Phenyl Me single bond p-NA SEQ ID NO:72 (73) Pro Leu Ser Glu 3,4-DCP Me single bond p-NA SEQ ID NO:73 (74) Val Leu Ser Glu 4-Cl-Phenyl Me single bond p-NA SEQ ID NO:74 (75) D-Ala Asn Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:75 (76) D-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:76 (77) β-Ala Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:77 (78) γ-Abu Leu Ser Glu 2-Naphthyl Me single bond p-NA SEQ ID NO:78 (79) Leu Ser Glu 2-Naphthyl Me Leu p-NA SEQ ID NO:79 (80) Leu Ser Glu 2-Naphthyl Me Ala p-NA SEQ ID NO:80 (81) Leu Ser Glu 2-Naphthyl Me Gly p-NA SEQ ID NO:81 (82) Sar Leu Ser Glu 2-Naphthyl Me Ala p-NA SEQ ID NO:82 (83) Sar Leu Ser Glu 2-Naphthyl Me Gly p-NA SEQ ID NO:83 (84) Sar Leu Ser Glu 2-Naphthyl Me Ala m-ASD SEQ ID NO:84 (85) Sar Ser Gly 2-Naphthyl Me Ala DCHA SEQ ID NO:85

in Table 1, the meaning of each abbreveated symbol is as follows: Me=methyl, Et=ethyl, n-Pr=n-propyl, Ac=acetyl, Sar=N^(α)-methyl-glycine, Me-Val=N^(α)-methyl-valine, Me-Ala=N^(α)-methyl-alanine, γ-Abu=γ-aminobutanoic acid, p-NA=p-nitroaniline residue, 3,4-DCP=3,4-dichlorophenyl, m-ASD=m-anisidine residue, DCHA=3,5-dichloro-4-hydroxyaniline residue.
 8. A method for assaying human pepsinogen II or human pepsin II characterized by digesting a peptide of the formula (I) depicted in claim 1, wherein all the symbols are as defined in claim 1, or an acid addition salt thereof, by human pepsin II which is obtained by activation of human pepsinogen II in a sample or human pepsin II in a sample to obtain an amino acid derivative of the formula (II)

wherein all the symbols are as defined in claim 1, digesting the obtained amino acid derivative of the formula (II) by aminopeptidase to obtain an aniline, aminocoumarine or aminonaphthalene derivative of the formula Z—H, and then detecting the obtained aniline, aminocoumarine or aminonaphthalene derivative.
 9. A method for assaying according to claim 8 using a peptide of the formula (I-A) depicted in claim 7 (wherein all the symbols are as defined in claim 7) or an acid addition salt thereof.
 10. A kit for assaying human pepsinogen II or human pepsin II which is characterized by comprising a peptide of the formula (I) as depicted in claim 1 (wherein all the symbols are as defined in claim 1) or an acid addition salt thereof as a substrate and aminopeptidase.
 11. A peptide according to claim 1, wherein m+n is an integer of 1 or more. 